Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/62—Plasma-deposition of organic layers
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/28—Materials for coating prostheses
  • A61L27/34—Macromolecular materials
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L33/00—Antithrombogenic treatment of surgical articles, e.g. sutures, catheters, prostheses, or of articles for the manipulation or conditioning of blood; Materials for such treatment
  • A61L33/06—Use of macromolecular materials
  • A61L33/068—Use of macromolecular materials obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/14—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by electrical means
  • B05D3/141—Plasma treatment
  • B05D3/142—Pretreatment

Definitions

• the present invention relates to methods of coating surfaces so that they are substantially inert and in particular are biocompatible. Further aspects of the invention include coated surfaces and articles which carry these coatings.
• Inert surfaces are required in a number of applications.
• chemicals are passed through conduits and stored in storage facilities in contact with the walls of the vessels. Over a period of time, reactive chemicals may erode or leach into the surface of the walls, causing contamination of the chemical by material from the surface and loss of chemical into the walls. This may be a particular problem in, for example, the pharmaceutical industry.
• containers or bottles used to hold or store these pharmaceutical chemicals should have resistant or inert surfaces.
• Biocompatible surfaces are particularly important in medical apparatus.
• apparatus is used herein to encompass medical devices such as implants and prosthetics such as arterial valves which are in contact with the blood for extended periods of time as well as components such as tubing conduits, or other parts of an extracorporeal circulation circuit used, for example, in dialysis and cardio-surgery.
• the components used in these circuits are generally made of substantially inert polymeric materials such as plastic or elastomeric materials with varying levels of biompatibility. Consequently, they may be involved in adverse biological reactions. Such reactions may lead to a postperfusion syndrome experienced by certain patients.
• biocompatibility of these apparatus is mainly a result of their specific surface properties
• changing the surface composition, for example, by applying or grafting on more biocompatible material may enhance their biocompatibility and improve the final patient comfort.
• coatings are produced by placing the substrate to be coated within a reactor vessel at low pressure and subjecting it to a plasma discharge. The effect that this has on the surface depends upon the gaseous material present within the reactor during the plasma discharge.
• the surface is subjected to a plasma discharge for an extended period of time in the presence of an inert gas, it will become etched. Reagents may subsequently be grafted onto the surface, optionally under the influence of a plasma discharge.
• US Patent No. 4656083 describes a plasma discharge process in which a fluorocarbon layer is deposited onto the surface of a biomedical device, in order to enhance its biocompatibility.
• a method for pretreating the surface of a medical device so as to deposit a polymeric adhesive layer using plasma polymerisation or grafting methods is described in US Patent No. 5451428.
• a biological coating and in particular an anti-thrombogenic material is subsequently applied in a further step and adhers to the deposited adhesive layer.
• US Patent No 5326584 describes a method of permanently modifying the surface of a substrate material by using plasma etching followed by a grafting of a material which is similar to the substrate material.
• the grafting process is induced by a second radio frequency plasma. It is suggested that this method could be employed to modify the surface of silicone elastomers by grafting hexamethyldisiloxane onto a previously etched surface.
• the invention provides a method of applying an inert coating to a surface, said method comprising in a first step, subjecting the surface to a plasma discharge in the presence of an inert gas for a period sufficient to activate the surface, and in a subsequent step, contacting the activated surface with a gaseous organosilicon material which reacts with the activated surface in the absence of plasma so as to deposit said organosilicon material on the surface.
• the organosilicon material on the surface may be continuous or discontinuous but is sufficient to reduce the reactivity of the surface and increase its biocompatibility.
• Suitable gases for use in the first stage of this process are inert gases, such as argon, neon, krypton or xenon, as well as other gases such as nitrogen or carbon dioxide, and also oxygen.
• inert gases such as argon, neon, krypton or xenon
• other gases such as nitrogen or carbon dioxide, and also oxygen.
• an inert gas, in particular argon is used.
• it is suitably exposed to the plasma gas discharge for a period of between about 5 seconds to about 30 minutes.
• the plasma discharge process of the first step of the method of the invention is suitably effected in a reactor equipped with a radio frequency generator capable of generating a frequency of about 1 MHz to about 40 MHz and preferably 13.56 MHz.
• a microwave generator generating a frequency of about 233 MHz to about 466 MHz can be used.
• the power delivered is about 25 W to about 200 W and preferably about 100 W.
• Suitable organosilicon materials used in the second step of the process of the invention are materials which, when in a gaseous form, react with the activated surface produced in the first step of the method of the invention to deposit the organosilicon material on the surface. Typically, this reaction occurs in the absence of plasma by way of a functional group such as hydrogen or an unsaturated group attached to a silicon.
• the organosilicon materials can be gaseous at ambient temperature or they can be converted to a vapor by heating to temperatures up to 200°C, and preferably 50°C or less.
• the organosilicon materials have a vapor pressure of at least 0.1Hgmm at room temperature.
• organosilicon materials include organosilanes and organosiloxanes.
• organosilanes include materials of formula (I): R 1 n SiR 2 m wherein each group R 1 is independently selected from the group consisting of hydrogen or optionally substituted alkenyl; each group R 2 is independently selected from an optionally substituted alkyl group of 1 to 20 carbon atoms; or a group (OR 3 ) or (OSiR 3 3 ), where each R 3 is independently an optionally substituted alkyl group of 1 to 20 carbon atoms; n is an integer of 1 to 3; m is an integer of 1 to 3 and n + m is 4.
• Specific silanes can contain the same or different R 1 groups, e.g., vinyl and hexenyl groups, and/or different R 2 groups, e.g., methyl groups and (OSiR 3 3 ) groups.
• organosiloxanes examples include materials of the structure (II) R 1 a R 2 (3-a) Si (OSiR 4 2 ) x OSiR 1 b R 2 (3-b) wherein each R 1 and R 2 are as defined above, each group R 4 is independently selected from the group consisting of hydrogen, optionally substituted alkenyl groups; optionally substituted alkyl groups of 1 to 20 carbon atoms and aryl groups, with the proviso that at least one R 1 or R 4 group per molecule is an unsubstituted alkenyl group or a hydrogen; a is 0, 1, 2, or 3 and b is 0, 1, 2, or 3,x is 0 or a positive integer, for example of from 1 to 20.
• the organosiloxanes can contain the same or different R 1 groups, e.g., vinyl and hexenyl groups, the same or different R 2 groups, e.g., methyl groups and (OR 3 ) groups, and/or the same or different R 4 groups, e.g., methyl groups and phenyl groups.
• R 1 groups e.g., vinyl and hexenyl groups
• R 2 groups e.g., methyl groups and (OR 3 ) groups
• R 4 groups e.g., methyl groups and phenyl groups.
• one R 1 group per molecule is an optionally substituted alkenyl
• R 2 is an optionally substituted alkyl
• R 4 is an optionally substituted alkyl such that the structure comprises R 1 SiR 2 2 (OSiR 4 2 ) x OSiR 2 3
• the R 2 and R 4 groups of this structure comprise substantially all methyl groups.
• alkyl refers to straight or branched chain groups, for example of from 1 to 20, suitably from 1 to 3 carbon atoms in length.
• alkenyl refers to straight or branched unsaturated hydrocarbon groups which include at least one carbon-carbon double bond and suitably from 2-20, preferably from 2-6 carbon atoms.
• Terms such as “alkoxy” will be interpreted as meaning an O-alkyl group as is conventional.
• Particularly suitable unsubstituted alkenyl groups R 1 include vinyl, hexenyl or allyl.
• a preferred group is vinyl.
• Suitable optional substitutents for alkyl and alkenyl groups R 1 R 2, R 3 and R 4 include halogen such as fluoro, preferably in the form of a perhaloalkyl group such as trifluoromethyl, oxo, alkoxy, amino or mono- or di-alkyl amino, or a silicon derivative such as an alkyl silane.
• halogen such as fluoro
• a perhaloalkyl group such as trifluoromethyl, oxo, alkoxy, amino or mono- or di-alkyl amino, or a silicon derivative such as an alkyl silane.
• a particular example of such a substituted alkyl group is 3,3,3-trifluoropropyl.
• R 2 , R 3 and/or R 4 are C 1-3 alkyl groups, such as methyl.
• At least one R 1 group or, where appropriate, R 4 is hydrogen or vinyl.
• compounds of organosilicon materials for use in the invention include vinylmethylbis (trimethylsiloxy)silane or vinylpenta-methyldisiloxane, vinylheptamethyltrisiloxane, vinyl tris (trimethylsiloxy) silane, trimethylsilane, and vinyltrimethylsilane, preferably vinylmethylbis (trimethylsiloxy)silane or vinylpenta-methyldisiloxane.
• the organosilicon materials can be diluted in a carrier gas for delivery to the activated surface.
• Suitable carriers include, for example, inert gases such as argon.
• the surfaces of materials suitable for use in the method of the invention are those which are able to support free radicals such as plastics and polymers.
• These materials include polycarbonates (PC), polyurethanes (PU), polypropylenes (PP), polyethylenes (PE)(including polytetrafluoroethylenes),polyvinylchloride (PVC), silicone elastomers, polyesters (such as polyethylene tetraphthalate), polymethylmethacrylate (PMMA) and polymers of hydroxyethylmethacrylate.
• PC polycarbonates
• PU polyurethanes
• PP polypropylenes
• PE polyethylenes
• PE polyethylenes
• PVC polyvinylchloride
• silicone elastomers polyesters (such as polyethylene tetraphthalate), polymethylmethacrylate (PMMA) and polymers of hydroxyethylmethacrylate.
• Preferred polymeric materials include silicone elastomers, PC, PVC, PU, PP
• Coatings derived from the deposition process of the present invention may comprise the organosilicon material directly attached to the surface or the organosilicon material or it may partially or fully polymerize prior to or during deposition. These coatings are often inert to many chemical reagents and therefore have a range of utilities where reaction between these reagents and surfaces is to be avoided. In particular however, the coatings described above have good biocompatibility. Thus they are particularly suitable for application to medical apparatus as outlined above, in particular to tubing and other components used in extracorporeal circulation circuits. Such apparatus will, in general, comprise the elastomeric or rigid plastics material outlined above.
• Organosilicon coatings applied using this process improve significantly both the biocompatibility and the thromboresistance of the treated materials.
• Coated surfaces obtainable by the method as described above, and articles which comprise such surfaces form a further aspect of the invention.
• the invention further provides a medical apparatus having an inert biocompatible coating thereon, said coating comprising an organosilicon material, grafted to a surface of the article.
• the organosilicon material is suitably derived from a volatile organosilicon material as described above.
• the apparatus suitably comprises an elastomeric or rigid plastics material which provides the substrate for the said inert coating.
• apparatus include medical devices like an implant or prosthesis for introduction into the body of a patient, or a component such as tubing used in extracorporeal circulation circuits
• the gaseous reagent was produced by heating the corresponding liquid at 50°C, and the gaseous product pushed towards the surface of the slab in the reactor using nitrogen gas. Each slab was exposed to the relevant vapours/and or gases for a period of 45 minutes at ambient temperature.
• the biocompatibility improvement of the slabs obtained in Example 1 was investigated using a coagulation test with bovine bloods in contact after total immersion of the untreated and treated materials. This test assesses globally the activation of the coagulation cascade which is a key parameter when it comes to evaluate the hemocompatibility of a material. The higher the coagulation time, the lower the coagulation activation, thus the better the biocompatibility of the material.
• the coagulation time of the untreated material was increased by 28% and up to 50% depending on the material used. This significant increase of the coagulation values with the coated material corresponds to a significantly lower thrombogenicity and higher biocompatibility.

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• Health & Medical Sciences (AREA)
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• 1999
  • 1999-07-30 EP EP19990306063 patent/EP0978324B1/de not_active Expired - Lifetime

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